.spinner-custom {
    display: none;
    width: 18px;
    height: 18px;
    border: 2px solid rgba(255,255,255,.3);
    border-radius: 50%;
    border-top-color: #fff;
    animation: spin 0.8s linear infinite;
    margin-left: 8px;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Active le spinner quand le bouton a la classe 'loading' */
.add-to-cart.loading .spinner-custom {
    display: inline-block;
}